However, in high-speed mode (3.4Mbps), one cycle is only ~5us, giving a max sample rate of 212kHz(!) Is this to fast for the arduino?
do I need a buffer on the SD card?
I2C high speed mode is 3.4Mhz.
I'm doing something like this, too. Is an I2C DAC too slow, or would a parallel one be necessary? Also, could the SDfatlib be used, or is that too slow?